Re: [PATCH v2 03/21] jbd2: point the shadow buffer at the frozen data directly

[Chris S]

You are right - I checked rather than taking my own word for it,
next-20260909 still has the unguarded dereference.

The fix is in, just not where linux-next takes its vfs branch from yet.
Christian folded the b_folio check into the commit that introduces the
folio-less buffer rather than carrying a separate patch, so on vfs.git's
vfs-7.4.bh branch 781bf9c7e307 ("buffer: allow a buffer_head to point at
memory outside the page cache") now reads

if (bh->b_folio && folio_test_dropbehind(bh->b_folio) &&
   op_is_write(opf))

That finished this morning.  linux-next merges vfs.all with tip is still
2026-09-02, so it carries the series without the fix - which is exactly
what you are hitting.  Should go away once vfs.all is regenerated.

Thanks,
Chao

On Thu, Sep 10, 2026 at 10:16 AM Bert Karwatzki <spasswolf@xxxxxx> wrote:
>
> Just a quick reminder, in linux next-20260909 this has not been
> fixed, yet.
>
> Bert Karwatzki